Question

If electron, hydrogen, helium and neon nuclei are all moving
with the velocity of light, then the wavelength associated
with these particles are in the order
(a) Electron > hydrogen > helium > neon
(b) Electron > helium > hydrogen > neon
(c) Electron < hydrogen < helium < neon
(d) Neon < hydrogen < helium < electron

Answer 1

If electron, hydrogen, helium and neon nuclei are all moving  with the velocity of light, then the wavelength associated  with these particles are in the order of  (a) Electron > hydrogen > helium > neon

Explanation:

To solve following problem consider the de-broglie equation.

λ = h/mv ..........(1)

λ = wavelength

h = planks constant

m = mass

v = velocity

All have same velocity i.e velocity of light and h is also constant. Thus equation (1) will be,

λ ∝ 1/m

The molar mass of given species in increasing order is e⁻ ∠ H ∠He∠Ne

wavelength and mass is inversely proportional to each other thus order of wavelength will be,

Electron > hydrogen > helium > neon